This invention relates to a tensioner which maintains a belt or a chain of an internal combustion engine in a suitable tension state.
In the tensioner, a tension rod energized by a spring force abuts against a belt, chain or the like, directly or indirectly through a pulley, thereby providing a fixed stress to the belt or the chain by the urged spring force. For this purpose, in a fundamental construction of the tensioner, a tension rod is provided in a casing so as to be able to be advanced. A spring for advancing the tension rod is provided in the casing.
However, since such tensioner is energized by a spring, there is the danger of unexpected advancement of the tension rod and the projecting from the casing of the tension rod before assembling of the device or at time of removing the tension rod from the device. For this purpose, the tensioner is provided with a stopper mechanism which locks the advancement of the tension rod. In the traditional stopper mechanism, a pin hole having a small diameter is formed in each tensioner and the casing. The advancement of the tension rod is locked by inserting the stopper pin into each pin hole of the tensioner and the casing in the connecting state of the pin hole.
After assembling the tensioner to the device, the urging operation of the tension rod due to the spring force is performed by withdrawing the stopper pin to remove the locking of the tension rod.
In the traditional stopper mechanism when the stopper pin is withdrawn, it is necessary to position the casing for inserting the stopper pin in the pin hole of the tension rod. However, this positioning is very difficult. Further, the locking portion of the stopper pin is only one portion with respect to the advancing direction of the tension rod and the locking of the tension rod at an arbitrary position is impossible.
Further, when the tension rod is advanced, the rod portion supported by the casing is decreased, which causes instability of the operation of the rod. This invention is an improvement in view of the above casses, and provides a tensioner where it is possible to lock the tension rod at an arbitrary position easily and securely by a simple operation.